Higher levels of CMR can improve weight gains, trial shows

Feeding bull calves higher rates of calf milk replacer (CMR) has been found to increase liveweight gains by almost 6kg by 12 weeks of age.

Harper Adams University carried out a study comparing the effect of feeding different rates of CMR to 40 British Blue x Holstein and Holstein bull calves, starting at 15.4 days old until weaning six weeks later. Performance to 12 weeks was subsequently monitored.

How the trial worked

One group of 20 calves was fed 900g of CMR a day mixed at a ratio of 180g to 820ml of water, with calves fed 2.5 litres twice a day.

The other half was fed 750g of CMR a day mixed at a ratio of 150g of powder to 850ml of water, with calves also fed 2.5 litres twice a day.

In both groups milk rates were reduced to one feed a day, consisting of 1.25 litres of milk by weaning at day 42. All calves were offered ad-lib 18% CP early weaning concentrates, water and straw, before moving into group pens at weaning.

Results

Calves fed 750g of CMR a day recorded average 12-week weights of 135kg – higher than recognised targets of 119-122kg.

However, this compared with 12-week average weights of 138.5kg in the group fed 900g a day, although these calves were 2.1kg lighter at the start on average. (The 750g and 900g calves had average start weights of 53.6kg and 51.5kg, but this was not statistically significant.)

Calves fed 750g put on 81.4kg from start to 12 weeks and the calves fed 900g put on 87.0kg.

Frame scores were higher for calves fed 900g. For example, calf wither height increased from 87.1cm to 88.4cm on average among calves feed the higher CMR.

Despite a widespread belief that feeding a higher rate of milk powder would lower concentrate intakes, no significant difference was recorded to weaning, with kilos of concentrate hitting 19.4kg in the group fed 750g a day, compared with 17.7kg in the group fed 900g.

The group fed 900g CMR had significantly higher DLWGs from start to weaning and by 12 weeks this equated to an extra 5.6kg.

Cost benefit

Despite the fact feed costs increased by 5p/kg LWG on the higher rate of powder, there was actually a cost benefit of 24p/kg because of improved health, with weaning costs falling from £1.66/kg LWG to £1.42/kg (see tables).

Health

Only two calves fed 900g required treating for disease, compared with six calves in the group fed the lower rate of CMR, lowering overall treatment costs from £4.59 a calf to just £1.55 a calf.

Beef cattle specialist Simon Marsh, who supervised the trial, says further cost benefits would probably be seen later on.

“This increase in feeding costs to 12 weeks would be recouped by valuing the extra 5.6kg liveweight gain at £2.13/kg.”

Mr Marsh says the reason calves fed the higher rate of powder were healthier and showed improved coat bloom scores was possibly that their immune status was better.

He says the study could be replicated in dairy heifers, adding: “The approach has always been to minimise milk powder because it is expensive. But across all the calf trials we have done, calves recording lower DLWGs never catch up.”

Therefore, he says, it is worth capitalising on the efficient, early growth phase.

Mr Marsh will next monitor subsequent bull performance and investigate whether the calves fed higher CMR will be slaughtered earlier or finish at heavier weights.